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The C, N and P content of surficial sediments, 210Pb-derived accumulation rates, and burial rates of C, N and P were determined in Lake Calado. Lake Calado is a dendritic lake located on the floodplain of the central Amazon basin, adjacent to the Solimoes river, just east of Manacapuru. A significant positive, linear relationship was found between distance from the river and C, N and P content of the sediments (r2 = 0.93, r2 = 0.92, p<0.001 for C and N, respectively, and r2 = 0.64, p<0.05 for P), indicative of high organic matter content on the floodplain and a greater proportion of clay near the river. Average sediment accumulation rates derived from two cores collected from each of three stations ranged from 41 to 117 mg cm-2 yr-1. Lake-wide, annual burial rates are estimated to be 3.5 mol C m-2, 0.28 mol N m-2 and 0.016 mol P m-2 .

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This archive consists of six comma-delimited ASCII files corresponding to the data tables published in (Smith, 2003). For the user's convenience, the original Microsoft Word file is provided as well to provide valuable information, formatting, and formulas that are lost in the conversion from MsWord to ASCII text.

Figure 1 in (Smith, 2003) shows the four sample site locations listed in the results tables.

These are identified simply as Site 1 through Site 4. The site indicated by an asterisk is a site where IRION (1982) collected a sediment core.

Using Figure 1 and Google Earth we estimated the geographic location of these sites to be as follows (note: Latitude and Longitude are given in decimal degrees with negative meaning these are south and west.):

Site Number,latitude,longitude,habitat,,,,,,,,,,,

1,-3.269,-60.583,open water,,,,,,,,,,,

2,-3.275,-60.580,open water,,,,,,,,,,,

3,-3.288,-60.578,open water,,,,,,,,,,,

4,-3.309,-60.570,open water,,,,,,,,,,,

5,-3.310,-60.570,open water,,,,,,,,,,,

6,-3.312,-60.569,open water,,,,,,,,,,,

7,-3.303,-60.565,open water,,,,,,,,,,,

8,-3.307,-60.554,open water,,,,,,,,,,,

9,-3.310,-60.548,open water,,,,,,,,,,,

10,-3.295,-60.558,streambed,,,,,,,,,,,

11,-3.312,-60.560,macrophyte,,,,,,,,,,,

asterisk,-3.290,-60.578,open water,,,,,,,,,,,

Approximate uncertainty is about 0.005 to 0.01 degrees.,,,,,,,,,,,,,,

Lago Calado is located on the north shore of the Solimoes River, east of the city of Manacapuru, in Brazil.

The site locations in this table were aproximated using Figure 1 and Google Earth, for the purpose of this archive, to describe the sites listed in the results tables.

Fig. 1: Map of Lake Calado located in Amazonas, Brazil (3 deg 5min S, 60deg 34 min W). The numbers on the map indicate the sampling sites of the sediment survey described in Table 2. Two sets of sediment cores were collected at sites 1, 3, and 4. The limit of the lake during the low water period lake is indicated by stippling, and the high-water extent of the lake is indicated by solid lines. Asterisk indicates site where IRION (1982) collected a sediment core

Data Description: The percentage of sand, silt, and clay in the 0-2 and 10-12 cm intervals, and surface porosity (A), and surficial particulate carbon, nitrogen, and phosphorus content (mol mg-1dry weight) in sediment cores (B) collected in Lake Calado. Standard deviations are based on the mean (n=2). If no standard deviation is provided, only one measurement was made.

Data Description: The percentage of sand, silt, and clay in the 0-2 and 10-12 cm intervals, and surface porosity (A), and surficial particulate carbon, nitrogen, and phosphorus content (mol mg-1 dry weight) in sediment cores (B) collected in Lake Calado. Standard deviations are based on the mean (n=2). If no standard deviation is provided, only one measurement was made.

Study Location: Lago Calado is located on the north shore of the Solimoes River, east of the city of Manacapuru, in Brazil.

Habitat: Open water

Column Number,Column Heading,Units,Variable Description,,,,,

1,Site,,Site numbers as shown in Fig.1 (Smith, et al., 2003) Site 1 is farthest from R.Solimoes,,,,,

Data Description: Carbon, nitrogen and phosphorus content (mol/mg dry weight) and molar C:N and N:P ratios of surficial sediments collected throughout L. Calado. Standard deviations are based on the mean (n=2). If no standard deviation is provided, only one measurement was made.. See companion file: Study_Site_Info.csv for location of site numbers. Type indicates where the samples were collected: open water (open), streambed (stream), or below macrophytes (macro).

Data description: Epilimnetic seston composition (microM) during the stratified period in Lake Calado. The values represent the mean of two samples collected at the sub-surface and above the hypolimnion. See Figure 1 for location of site numbers. [Smith 2003, Table 3]

3,Interval,cm,Interval of the sediment core; Where marked with a, isotope 226 Ra composite was used.,,,,

4,Cumulative_density,g/square_cm,Cumulative density,,,,

5,Total_210Pb,dpm/g,Total 210 isotope lead,,,,

6,Uncertainty,dpm/g,Uncertainty (plus or minus),,,,

Example file records:

Site,Year,Interval,Cumulative_density,Total_210Pb,Uncertainty,,

1,1982,2-3,0.25,32.8,1.4,,

1,1982,3-4a,0.36,29.0,1.0,,

1,1982,6-7,0.70,25.9,0.7,,

1,1982,7-8a,0.85,24.0,1.0,,

1,1982,11-12,1.37,20.4,1.0,,

1,1982,16-17a,2.01,17.2,1.0,,

1,1982,20-21a,2.52,14.7,0.9,,

1,1982,25-26,3.24,15.0,0.5,,

Data File #6:

Filename: Table5.csv,,,,,,,,,,,

Data Description: Measurements of 210Pb from cores collected in Lake Calado. 226Ra indicates the background level of radium used to estimate supported 210Pb. Excess 210Pb is the quantity of unsupported 210Pb within the surficial sediments. Accumulation rates of total dry weight (mg/square_cm/yr), which were derived from two models (CIC and CRS; Appleby and Oldfield, 1983), are also compared. 210Pb flux is the flux of 210Pb at the sediment-water interface (dpm/square_cm/yr). Uncertainties were calculated as mean standard error for each profile/sample size (n) and are provided as plus-or-minus 1 standard deviation, unless otherwise indicated. (Smith 2003, Table 5)

Definitions

Symbol,Definition,,,,,,,,,,

210Pb,lead isotope 210,,,,,,,,,,

226Ra,radium isotope 226; the background level of radium used to estimate supported 210Pb.,,,,,,,,,,

Excess 210Pb,The quantity of unsupported 210Pb within the surficial sediments is called the excess 210Pb.,,,,,,,,,,

Pb_Flux,The flux of 210Pb at the sediment-water interface (dpm/square_cm/year).,,,,,,,,,,

6,Acc_rate_CIC,mg/square_cm/yr,Accumulation rate of total dry weight, derived from CIS model,,,,,,,,,,

7,Acc_rate_CIC_SD,mg/square_cm/yr,Uncertainty of value in column 6, in plus or minus standard deviation,,,,,,,,,,

8,Acc_rate_CRS,mg/square_cm/yr,Accumulation rate of total dry weight, derived from CRS model,,,,,,,,,,

9,Acc_rate_CRS_SD,mg/square_cm/yr,Uncertainty of value in column 8. Fitting uncertainties were all <10%; an uncertainty of 20% is assigned for each profile and 14% for the mean. [Means are omitted from archive.],,,,,,,,,,

10,Pb_Flux_CIC,dpm/square_cm/yr,Flux of 210Pb at the sediment-water interface, from CIC model,,,,,,,,,,

11,Pb_Flux_CIC_SD,dpm/square_cm/yr,Uncertainty of value in column 10. The uncertainty of integrating an individual profile was estimated to be 15%.,,,,,,,,,,

Data description: Burial rates of carbon, nitrogen and phosphorus (mmol/square_cm/yr) for Lake Calado. (Smith 2003, Table 6). Burial rates of carbon, nitrogen and phosphorus across the 25 cm horizon were calculated as the product of the elemental content in the sediments between 20 and 30 cm and the sediment accumulation rate derived from the CRS model. Errors for individual cores were calculated as: SD = (AX)0.5 (Bevington 1969), where A = (SQ)2 and X = [(sds)2 /S2] + [(sdq)2 /Q2]; SD is the standard deviation of the burial rates; S is the sediment accumulation rate (CRS model, Table 5); Q is the quantity of C, N, or P in the surficial sediments, sds is the standard deviation of the sediment accumulation rate (S), and sdq is the standard deviation of the quantity of C, N, or P in the surficial sediments (Q).

Column Number,Column Heading,Units,Variable Description,,,,,,,,

1,Site,,Site numbers as shown in Fig.1 (Smith, et al., 2003) Site 1 is farthest from R.Solimoes,,,,,,,,

These results are derived from sediment cores collected from Lago Calado in 1982 and 1984.

Application

[Excerpt p.414, Smith,2003]

Our findings are a necessary component of mass balance analyses of carbon and nutrients for the Amazon floodplain and to evaluations of how land use changes may influence sedimentation rates on the floodplains.

Results from this work were used in (Engle,2007).

Quality Assessment (Data Quality Attribute Accuracy Report):

Quality Assessment:

Quality assessment for all reported values are shown in the data tables. [The below information is pasted from the file Smith_Amaz_2003_tables.doc, which is part of this dataset.]

Table 1. The percentage of sand, silt, and clay clay in the 0-2 and 10-12 cm intervals, and surface porosity (A), and surficial particulate carbon, nitrogen, and phosphorus content (mol mg-1dry weight) in sediment cores (B) collected in Lake Calado. The values in parentheses represent the standard deviation of the mean (n=2).

Table 3. Epilimnetic seston composition (Ãâï¿½ÃÂµM) during the stratified period in Lake Calado. The values represent the mean of two samples collected at the sub-surface and above the hypolimnion.

Table 4. Summary of 210Pb data for cores collected at Lake Calado. The + or - values are given to the right of column five.

Table 5. Measurements of 210Pb from cores collected in Lake Calado. 226Ra indicates the background level of radium used to estimate supported 210Pb. Excess 210Pb is the quantity of unsupported 210Pb within the surficial sediments. Accumulation rates of total dry weight (mg cm-2 yr-1), which were derived from two models (CIC and CRS; Appleby and Oldfield, 1983), are also compared. 210Pb flux is the flux of 210Pb at the sediment-water interface (dpm cm-2 yr-1). Uncertainties are given as Ãâï¿½ÃÂ±1 standard deviation, unless otherwise indicated.

Process Description:

Data Acquisition Materials and Methods:

Methods

An EKMAN dredge was used to collect sediments from eleven stations throughout L. Calado (Fig. 1): nine open water sites (sites 1-9), one stream site (site 10), and one site where emergent floating aquatic macrophytes occur during the high water period (site 11). Two separate casts were made per site, and a sub-sample of the top (approximately 2 cm) of material was collected in screw-top, glass bottles. These samples were returned to the University of California, Santa Barbara, and analyzed for carbon, nitrogen and phosphorus as described below.

One sediment core per site was collected in March, 1982, and in February, 1984, from three stations (1, 3, 4) located along the north to south axis of the lake (Fig. 1). The 1982 cores were collected with a piston corer (inside diameter of 3.8 cm) inserted into the sediments with rods from the surface. The 1984 cores were collected with a coring device consisting of polyvinylchloride plastic pipe (inside diameter of 10 cm) and a one-way valve. The overlying water within both corers was clear, indicating that the cores collected were undisturbed. After collection, the cores were processed immediately at a floating laboratory anchored in the middle of the southern portion of the lake. The 1982 cores were extruded and sectioned at 1 cm intervals, and the 1984 cores were extruded and sectioned at 1 cm intervals near the top and at 2 cm intervals elsewhere.

The water and solid masses were determined by weighing aliquots of wet sediment before and after drying at 80 degrees C. Only the central portion of each section was used for analyses.
The carbon and nitrogen content in the dried sediment samples was determined with a PERKIN-ELMER CHN analyzer. Phosphorus was measured by digestion in 1 N HCl after ignition for 1 hour at 550 degrees C (ANDERSEN 1976), followed by spectrophotometric determination of orthophosphate (STRICKLAND & PARSONS 1972). The method of FOLK (1969) was used to determine the sand, silt and clay fractions of the 0-2 cm and 10-12 cm intervals. The sediment samples were dispersed with a 5 grams per liter solution of Calgon and sieved through a 64 micron sieve. The proportion remaining in the sieve was considered the sand fraction. The silt (5-63 micron) and clay (<5 micron) fractions were determined by pipette analysis based on settling time.

The determination of 210Pb was based on the measurement of 210Po, the 210Pb granddaughter that is assumed to be in secular equilibrium with its grandparent. This assumption should be satisfactory because both isotopes should have low solubility in these low salinity waters, and because several months elapsed between sample collection and analysis. The analysis followed procedures outlined in FULLER (1982). Dried sediment (0.2-1.0 g) and a spike of 5-20 dpm of 208Po were placed in a Teflon beaker. Solid phases were totally dissolved by sequential leaching with concentrated hydrochloric, nitric plus perchloric, and hydrofluoric acids. After the sample was dissolved, it was dried, and the residue was dissolved in 1 N HCl. Ascorbic acid was added to complex iron, and polonium isotopes were spontaneously electroplated onto a silver disk. Activity on the disk was counted in an alpha spectrometer to measure the ratio of 210Po to 208Po. Solutions remaining after plating were stored, and selected samples were combined for analysis of 226Ra, measured by in-growth of 222Rn and alpha scintillation procedures (HAMMOND & FULLER 1979).

The elemental composition of seston located within the epilimnion was determined on a monthly basis during the period of thermal stratification (February-August 1984). One-liter water samples were collected with a VAN DORN sampler at the sub-surface and above the hypolimnion, filtered in duplicate onto tarred pre-combusted 45 mm GELMAN AE glass-fiber filters and dried at 80 degrees C.